One of the world's leading neurosurgeons testified Wednesday that a San Jose motorist charged with killing two elderly pedestrians in an apparent fit of drunken road rage could have been unaware of his murderous conduct because of pressure on his brain from an intracranial cyst.

The jury leaned in to listen to the novel explanation by Dr. Knut Gustav Wester, who flew in from Norway to testify for free over a two-day period in Armando Ochoa's trial.

Ochoa, 49, is facing a maximum sentence of about 45 years to life in prison if he is convicted in Santa Clara County Superior Court of killing Aproniano Siruno, 71, and Rodolfo Escurial, 67. He also badly injured Esteban Casiano, 73, when he ran all three of them down with his white SUV while he was extremely drunk.

Wester, a slender 72-year-old professor of neurology with piercing blue eyes and a neatly trimmed white beard and mustache, noted that an MRI taken at a Kaiser Permanente hospital before the collision revealed a watery "arachnoid'' cyst atop Ochoa's left temporal lobe.

Pressure from that spiderlike growth could have reduced the circulation of blood in Ochoa's brain, triggering a series of severe anxiety attacks on Sept. 14, 2008, that left Ochoa unaware he'd been in a fatal collision that day, the doctor contended.

"An anxiety attack may be so strong that the person for all practical purposes loses consciousness,'' Wester said.

No symptoms

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But under cross-examination by prosecutor Daniel H. Fehderau, Wester acknowledged he never physically examined or interviewed the unemployed commercial painter, who has been locked up in jail for the past four years.

Nor has any other doctor ever put Ochoa through the battery of tests required to determine if the cyst has indeed left him cognitively impaired.

"There are differences of medical opinion about whether all cysts are symptomatic, right, doctor?'' Fehderau asked.

Wester agreed, adding "my view (that many arachnoid cysts do cause symptoms) is different than almost any other neurosurgeon in the world.''

But the doctor also stopped short of agreeing with Ochoa's lawyer, Ingo Brauer, that the defendant may well have been having an epileptic attack triggered by the cyst. Epilepsy can be a symptom of arachnoid cysts, but anxiety attacks are a more common side effect and better fit Ochoa's behavior, Wester said.

Ochoa had complained to Kaiser as far back as 1998 about headaches, and later about depression and anxiety. The cyst, which he was born with, was accidentally discovered during an MRI before the collision, which Ochoa underwent because of a possible nose fracture.

He was told the cyst was "stable'' and not the cause of any symptoms, as is the case with the majority of people worldwide with such cysts, the prosecutor noted.

Rage eruption

But Wester testified that Ochoa was never tested to determine if the cyst was impairing his brain function or not. He also said that symptoms can arise rapidly, for instance, after a severe bump on the head.

Ochoa was hospitalized for five days in March 2007, about 19 months before the collision, after complaining of headaches, vomiting and painful urination. But it turned out he was suffering from pneumonia, a common problem among alcoholics. Wester noted that patients with anxiety often self-medicate using alcohol.

After the collision with the three elderly victims, the unemployed painter had a blood-alcohol level more than three times the legal limit. That is one reason he is charged with two counts of murder and one count of attempted murder rather than vehicular manslaughter.

Also, Ochoa had been up all night drinking, and then he argued with his family so vociferously a neighbor called the police. He had a beer with breakfast afterward, ignored a warning by a restaurant manager not to drive, erupted into road rage with a bewildered motorist, argued with a group of soccer players and threatened to kill someone right before he actually did, witnesses said.

Before plowing into the men, he also had racked up 10 speeding tickets, four drunken driving convictions and one hit-and-run accident.

Ochoa is expected to testify when the trial resumes after the holidays.